Base-Promoted Ammonia Borane Hydrogen-Release
Journal Article
·
· Journal of the American Chemical Society, 131(39):14101-14110
The strong non-nucleophilic base bis(dimethylamino)naphthalene (Proton Sponge, PS) has been found to promote the rate and extent of H2-release from ammonia borane (AB) either in the solid state or in ionic-liquid and tetraglyme solutions. For example, AB reactions in 1-butyl-3-methylimidazolium chloride (bmimCl) containing 5.3 mol % PS released 2 equiv of H2 in 171 min at 85 °C and only 9 min at 110 °C, whereas comparable reactions without PS required 316 min at 85 °C and 20 min at 110 °C. Ionic-liquid solvents proved more favorable than tetraglyme since they reduced the formation of undesirable products such as borazine. Solid-state and solution 11B NMR studies of PS-promoted reactions in progress support a reaction pathway involving initial AB deprotonation to form the H3BNH2 - anion. This anion can then initiate AB dehydropolymerization to form branched-chain polyaminoborane polymers. Subsequent chain-branching and dehydrogenation reactions lead ultimately to a cross-linked polyborazylene-type product. AB dehydrogenation by lithium and potassium triethylborohydride was found to produce the stabilized Et3BNH2BH3 - anion, with the crystallographically determined structure of the [Et3BNH2BH3]-K+ · 18-crown-6 complex showing that, following AB nitrogen-deprotonation by the triethylborohydride, the Lewis-acidic triethylborane group coordinated at the nitrogen. Model studies of the reactions of [Et3BNH2BH3]-Li+ with AB show evidence of chain-growth, providing additional support for a PS-promoted AB anionic dehydropolymerization H2- release process.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 979503
- Journal Information:
- Journal of the American Chemical Society, 131(39):14101-14110, Journal Name: Journal of the American Chemical Society, 131(39):14101-14110 Journal Issue: 39 Vol. 131; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
Similar Records
Solid-State NMR Study of Li-Assisted Dehydrogenation of Ammonia Borane
Probing the second dehydrogenation step in ammonia-borane dehydrocoupling: characterization and reactivity of the key intermediate, B-(cyclotriborazanyl)amine-borane
Iridium Catalyzed Dehydrogenation of Substituted Amine Boranes: Kinetics, Thermodynamics and Implications for Hydrogen Storage.
Journal Article
·
Wed Mar 21 00:00:00 EDT 2012
· Inorganic Chemistry
·
OSTI ID:1044998
Probing the second dehydrogenation step in ammonia-borane dehydrocoupling: characterization and reactivity of the key intermediate, B-(cyclotriborazanyl)amine-borane
Journal Article
·
Wed Oct 29 20:00:00 EDT 2014
· Chemical Science
·
OSTI ID:1624910
Iridium Catalyzed Dehydrogenation of Substituted Amine Boranes: Kinetics, Thermodynamics and Implications for Hydrogen Storage.
Journal Article
·
Mon Oct 06 00:00:00 EDT 2008
· Inorganic Chemistry, 47(19):8583-8585
·
OSTI ID:946629